1. Field
The present disclosure relates to an organic light-emitting diode (OLED) display apparatus and a method of manufacturing the same.
2. Description of the Related Art
In general, an organic light-emitting diode (OLED) display is a self-emissive display device that electrically excites fluorescent organic compounds, to emit light. An OLED display can be driven at a low voltage, and can have a small thickness, a good viewing angle, and a fast response speed. Thus, OLED displays are considered to be the next-generation of display devices, which overcome the problems associated with liquid crystal devices.
In an OLED, an organic light-emitting layer, in the form of a functional thin film, is inserted between an anode electrode and a cathode electrode. Holes are injected from the cathode electrode, and electrons are injected from the anode electrode. As the electrons and holes are combined in the organic light-emitting layer, excitons are formed, and light is emitted as the excitons return to a ground state.
OLED display apparatuses are divided into a bottom emission-type, in which light is emitted toward a substrate, and a top emission-type, in which a light is emitted away from a substrate. If a thin-film transistor (TFT) is mounted in a bottom emission-type OLED display apparatus, a surface from which light is emitted, that is, an aperture rate, may be limited, due to a large surface area of the TFT on the substrate. On the other hand, a top emission-type OLED display apparatus has a large light emitting area regardless of a TFT surface area, and thus, has a large aperture rate.
When manufacturing the top emission-type OLED display apparatus, a reflection layer is formed under the anode electrode that is electrically connected to a source electrode or a drain electrode of a TFT, in order to increase light extraction. However, due to microcavity effects, between the reflection layer, the anode electrode, and the cathode electrode, color wavelengths may be split, and the luminance or the color coordinates of the colors may vary. Also, when etching the reflection layer using a wet etching solution, metals included in the reflection layer may be damaged, due to penetration of the etching solution.
In order to prevent the microcavity effects, buffer layers are formed on an organic layer, between the anode electrode and the cathode electrode, to adjust a distance between the anode electrode and the cathode electrode, so as to form an appropriate resonance structure. In order to form buffer layers having different thicknesses for R, G, and B colored sub-pixels, different deposition masks are used, and thus, an increased amount of organic materials are consumed.